Reference electrodes including silicone-containing polymer and ionic liquid

Abstract

Reference electrodes that include a solid electron conductor; an interlayer; and a polymeric membrane layer comprising a polymer composition, the polymer composition comprising at least one silicone-containing polymer and at least one ionic liquid, wherein the polymeric membrane layer and the polymer composition are essentially plasticizer free and the silicone-containing polymer and the ionic liquid are miscible as determined using a thermodynamic method that shows a single glass transition temperature (Tg) of a composition including the at least one silicone-containing polymer and the at least one ionic liquid, wherein the interlayer is disposed between the solid electron conductor and the polymeric membrane layer. Also disclosed are electrochemical measurement systems including such reference electrodes.

The invention claimed is: 
     
       1. A reference electrode comprising:
 a solid electron conductor; 
 an interlayer; and 
 a polymeric membrane layer comprising a polymer composition, the polymer composition comprising at least one silicone-containing polymer and at least one ionic liquid, wherein the polymeric membrane layer and the polymer composition are essentially plasticizer free and the at least one silicone-containing polymer and the at least one ionic liquid are miscible, 
 wherein the interlayer is disposed between the solid electron conductor and the polymeric membrane layer. 
 
     
     
       2. The reference electrode according to  claim 1 , wherein the ionic liquid comprises at least one imidazolium cation or quaternary ammonium cation group; and an anion comprising a bis(perfluoroalkylsulfonyl)imide, an alkyl(perfluoroalkyl)sulfonylimide, a bis(alkylsulfonyl)imide, or a bis(alkylsulfonyl)imide anion with one or more ether, ester or amide groups interrupting the alkyl chain. 
     
     
       3. The reference electrode according to  claim 1 , wherein the ionic liquid is selected from 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C 8 mim + ][NTf 2   − ]), 1-methyl-3-decylimidazolium bis(trifluoromethylsulfonyl)imide ([C 10 mim + ][NTf 2   − ]), 1-methyl-3-dodecylimidazolium bis(trifluoromethylsulfonyl)imide ([C 8 mim + ][NTf 2   − ]), tributylmethylammonium bis(trifluoromethylsulfonyl)imide ([NBu 3 Me + ][NTf 2   − ]), and combinations thereof. 
     
     
       4. The reference electrode according to  claim 1 , wherein the polymer composition has from 5 to 75 wt % of the ionic liquid based on the total weight of the polymer composition. 
     
     
       5. The reference electrode according to  claim 1 , wherein the polymer composition has from 10 to 40 wt % of the ionic liquid based on the total weight of the polymer composition. 
     
     
       6. The reference electrode according to  claim 1 , wherein the polymer composition has from 10 to 30 wt % of the ionic liquid based on the total weight of the polymer composition. 
     
     
       7. The reference electrode according to  claim 1 , wherein the at least one silicone-containing polymer has a glass transition temperature lower than 20° C. 
     
     
       8. The reference electrode according to  claim 1 , wherein the at least one silicone-containing polymer is polysiloxane-based. 
     
     
       9. The reference electrode according to  claim 1 , wherein the at least one silicone-containing polymer is a polysiloxane-based fluorine-containing polymer, a polysiloxane-based methyl group-containing polymer, a polysiloxane-based cyano group-containing polymer, or a combination thereof. 
     
     
       10. The reference electrode according to  claim 1 , wherein the at least one silicone-containing polymer is poly([3,3,3-trifluoropropyl]methylsiloxane). 
     
     
       11. The reference electrode according to  claim 1 , wherein the polymer composition has from 5 to 50 wt % of the polymer based on the total weight of the polymer composition. 
     
     
       12. The reference electrode according to  claim 1 , wherein the polymer composition has from 10 to 30 wt % of the polymer based on the total weight of the polymer composition. 
     
     
       13. The reference electrode according to  claim 1 , wherein the polymer composition further comprises at least one kind of inorganic filler. 
     
     
       14. The reference electrode according to  claim 13 , wherein the at least one kind of inorganic filler is selected from a group consisting of silica and titanium dioxide. 
     
     
       15. The reference electrode according to  claim 1 , wherein a composition consisting essentially of the at least one silicone-containing polymer and the at least one ionic liquid has a single glass transition temperature (T g ) according to a thermodynamic method is selected from differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), thermal mechanical analysis (TMA), dynamic mechanical analysis (DMA), and dielectric thermal analysis (DETA). 
     
     
       16. The reference electrode according to  claim 15 , wherein the thermodynamic method is differential scanning calorimetry (DSC). 
     
     
       17. The reference electrode according to  claim 1 , wherein the polymeric membrane is solvent cast, spin-coated, dip-coated, or inkjet-printed from the polymer composition. 
     
     
       18. The reference electrode according to  claim 1 , wherein the solid electron conductor comprises silver, gold, platinum, copper, stainless steel, carbon, indium-tin-oxide (ITO), fluorine-doped tin oxide (FTO) or aluminum. 
     
     
       19. The reference electrode according to  claim 1 , wherein the reference electrode provides sample-independent and long-term stable electric potential of a potassium ion concentration at 4.1 mM. 
     
     
       20. An electrochemical measurement system comprising the reference electrode described in  claim 1 .